Process of forming images.



No. 772,471. PATENTBD OCT. 18, 1904. U. NEHRING.

PROCESS OF FORMING IMAGES.

APPLWATION FILED FEBA. 1804.

N0 MODEL.

WITNESSES: M07 [Vi 5M6 INVENTOR UNITED STATES Patented October 18, 1904.

ULRlUl-l NEHRING, OF NEW YORK, N. Y.

PROCESS OF FORMING IMAGES- SPECIFICATION forming part of Letters PatentNo. 772,471, dated October 18, 1904.

Application filed Efebruery 4,1804. Serial No. 191.983. (No model.)

To It volume it may concern; 1

Be it known thatl, ULRICH Nnunmo, a citinon of the United States,residing in New York, in the county of New York and State of New York,have invented new and useful improvements in Forming Images, of whichthe following is a specification.

The present invention relates to the correction of certain welhlrnowndefects in the use of rays-gathering means, such as spherical orparabolical surfaces or lenses, when used in forming images forphotographic or other purposes. i

It is known in optics that, for instance, a lens may be regarded aseonsistingof a series of concentric ringshaped elements, each having itsown focus. The distance of these foci from the optical center of thelens decreases along the optical axis of the lens as the diameter of thelens increases. In the case of spherical lenses orsuriaccs this fact isknown as spherical aberration." It is also known that thevariously-colored rays formingwhite light are of different wave lengthand amplitude of vibration, and therefore are of difierentrefrangibility; The violet rays, for instance, being the mostrefrangible, form a fo-' cus nearest to the lens, whereas the red rays,the least refrangible. have their focus farthest from the lens. Thisdeviation of foci is known as chromatic aberration.

Before attempting to enter into the subjectrnatter of the presentinvention it is thought to be advisable to state that the focus of alens is that point in the optical axis of the lens in which parallelrays meet after emergence and that the focal distance of a lens is thedistance between the focus of the lens and the optical center of thelens. The equivalent focus of a lens set or that point in the opticalaxis of the plurality of lenses forming the set or the system in whichparallel rays meet after passing all the lenses, and the equivalentfocal distance is the distance between the equivalent focus of the lensset or the lens system and the optical center of a theoretical orphantom lens representing the joint action of the plurality of lensesforming the entire system. It is to be noted that in optical vernacularthe words a lens system is focus and fecal distance have becomesynonymous.

The above-named defects of rays-gathering means become particularlyapparent. in photography and are the cause of producing 5 5 images whichwhen acting upon light-sensi tive surfaces, such as photographic platesor films, result in pictures having either difi'erently sharp ordistorted portions or not showing a true and correct color value of theoriginal object. Attempts have been made to overcome these defects,consisting in very? the distance between the rays gathering means andthe surface upon which the lightrays are proposed to act. It is obviousthat' such a procedure is not capable of changing the focus or focaldistance of the raysgathering means, but simply moves the focus alongthe. optical axis and leaves the distance of the focus from the opticalcenter of the raysgathering means undisturbed. A variation, in fact, ofthe focus of, for instance, a lens canbe produced only by varyingthedegree of refraction of the lens, or, in other words, by changing itsoptical properties.

The purpose of the present invention is to produce this efieet, and itis to be accomplished by either changing the distance between theindividual lenses or sets .of lenses forming an entire photographic lensor objective or by interpolating an auxiliary lens for this purpose,which in either case causes a change or variation of the focus.

The change of the distance between the lenses of a photographicobjective may be 5 brought about by, for instance, holdingone of thelenses stationary and movingthe other lens during the time of exposureto or from the stationary lens. Another 1 form of arrangernent would bethe use of a coiled spring between the lenses and properly connected tothe casing holding the same and a releasing device for said coiledspring. A third form would be to use a coiled spring outside of one ofthe lenses and a releasing device which 95 would cause one lens to moverelatively'to the other during the time of exposure. A fluidpressuredevice could also be used for this purpose. In this case a double casingfor holding the lenses may be provided containing oil, air, glycerin,&c., or any other fluid in the space between the casings and a devicefor increasing or decreasing the pressure of this fluid, whereby thedistance between the lenses would be varied.

Instead of varying the focus by changing the distance between thelenses, as stated hereinbefore, an auxiliary lens may be providedsecured to the front, the rear, or between the lenses of the objectiveto a point or pivot on the periphery of the lens-casing. This lens by asuitable arrangement may gradually be moved at right angles across andthrough the optical axis of the objective.

In the drawings, Figure 1 is a side view, partly in section, of a lensaccomplishing the object of the present invention by mechanical means.Fig. 2 is a front view of the lens illustrated in Fig. 1, and Fig. 3 isa front view of a lens accomplishing the object of the present inventionby optical means.

1 in the drawings is the outer casing or barrel of a lens system, whichcarries a stationary lens or lens set 2. 3 is the inner casing orbarrel, carrying another lens or lens set 4. The inner casing istelescoping the outer casingi. 0., is movable in the axis thereof. In asuitable space between the two casings is an elastic or resilient means5, which when operating causes a change of the distance between thelenses or lens sets forming the entire system, and consequently causinga change or variation of the focus and a decrease or increase of thefocus or the focal distance.

6 is a packing, washer, or stuiiing preferably adjustable for preventingany sudden movement of the inner casing 3 in relation to the outercasing 1. This packing may be saturated with oil or glycerin or othersuitable substances.

7 is a holding and releasing device operated by the pneumatic cylinder8, as well known in the art. The release 7 consists of a detent securedto the outer casing 1 and cooperating with teeth provided on the innercasing 3. This device is fully described and claimed in my United StatesPatent No. 756,881, of April 12, 1904, and covers a mechanical devicefor changing or varying the focus of rays-gathering means, such as alens.

An optical device for changing or varying the focus of rays-gatheringmeansis described and claimed in my United States Patent No. 761,390, ofMay 31, 1904. Fig. 3 of the drawings of the present application is aduplicate of part of the drawings of said United States patent andillustrates one form of such an optical device. 3 is the casing,carrying the lens or lens set 4 and a support 9, to which is pivotallysecured an auxiliarylens or lens set 10, controlled by a pneumaticdevice 8,-which causes the auxiliary lens orlens set 10 to move into orout of cooperative relation with the lens or lens set 4.

The practical application of the underlying method of forming images isas follows: An object is focused upon the sensitive surface in theordinary way. During the time of using the lens system one lens or lensset of the same is caused to move to or from the stationary lens or lensset, or the auxiliary lens herein mentioned is gradually moved acrossthe lenses of the entire lens system. In either case the focus of thesystem is varied or changed during the time of using the same, and inphotography an image can be produced, being evenly sharp and undistortedand lacking the defects due to spherical as well as chromaticaberration.

It is intended to be understood that the hereinafter claimed method offorming images comprises the forming of images for the purposes ofphotography, as well as for any other purpose, and includes thecorrecting of spherical aberration as well as of chromatic aberration.

The term lens used in the claims refers to any equivalent of a lens,single or corrpound,such as spherically or otherwise curved, reflectingsurfaces or refracting bodies.

What is claimed as new and useful, and de sired to be secured by UnitedStates Letters Patent, is

1. The method of forming images which consists in varying or changingduring the time of using a lens or lens set, the focus or focal distanceof the same.

2. The method of forming images which consists in gradually varying orchanging during the time of using a lens or lens set, the focus or.focal distance of the same.

3. The method of forming images which consists invarying or changingduring the time of using a plurality of lenses or lens sets, theequivalent focus or focal distance of the same.

4. The method of forming images which consists in gradually varying orchanging during the time of using a plurality of lenses or lens sets,the equivalent focus or focal distance of the same.

Signed at New York, in the county of New York and State of New York,this 1st day of February, 1904.

ULRICH NEHRING. In presence of MORRIS RUBENS, FREDERICK BRITSCH.

